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 March 3rd, 2010, 12:57 PM #1 Newbie   Joined: Mar 2010 Posts: 1 Thanks: 0 Is this possible? Hi all. Is it possible to find the point [x,y] if I know all the other variables on this diagram ([a,b], [c,d], length 1, length 2 and length 3)... It's been quite a long time since I studied Maths so any help would be massively appreciated. It's to solve some Javascript code in some animation in case you're interested or if it helps to find a solution. Thanks, JimJam http://www.jimjamgraphics.com/
March 3rd, 2010, 03:13 PM   #2
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Re: Is this possible?

Quote:
 Originally Posted by JimJamGraphics Is it possible to find the point [x,y] if I know all the other variables on this diagram ([a,b], [c,d], length 1, length 2 and length 3)...
Yes; it's just a bit messy. A little old fashioned technique helps, but it's still messy, so far as I can see, with a quadratic holding a number of literal constants [l1, l2 etc.]
l3 is redundant, as it is determined by the given coordinates.

Neat way to throw in a bit of advertising by the way.

 March 4th, 2010, 08:29 AM #3 Global Moderator   Joined: Dec 2006 Posts: 20,931 Thanks: 2205 It's length 1 that is redundant. The point (x, y) could lie on either side of the line joining the given points, so a little extra information is needed to reduce the two possibilities to just one.
March 4th, 2010, 09:14 AM   #4
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Re:

Quote:
 Originally Posted by skipjack It's length 1 that is redundant. The point (x, y) could lie on either side of the line joining the given points, so a little extra information is needed to reduce the two possibilities to just one.
Yes, that is the one I meant, obviously. I really should have taken typing more seriously. In any event, the point is that it is possible, but messy, and so needs only someone to spend the time.

March 4th, 2010, 10:07 AM   #5
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Re: Is this possible?

Hello, JimJam!

Quote:
 Is it possible to find the point [x,y] if I know all the other variables on this diagram ([a,b], [c,d], length 1, length 2 and length 3)

You should redraw the diagram . . . The point are collinear.

Code:
    (a,b)   (c,d)           (x,y)
*-------*---------------*
: - 1 - : - - - 2 - - - :
: - - - - - 3 - - - - - :

$\text{Then: }\;\begin{array}{ccc}x=&3c-2a \\ \\ \\ y=&3d-2b \end{array}=$

 March 4th, 2010, 04:56 PM #6 Global Moderator   Joined: Dec 2006 Posts: 20,931 Thanks: 2205 That interpretation may be too literal. I interpreted "length 1" as meaning "variable 1", etc., so that the three lengths are given by three variables.

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